Recommendations for 'soapsuds' to use spray plants with tons of aphids on them please?

Hi,

Researching the ongoing problem with aphids on my Buddeliah, which are now turning the lovely new leaves curly, lead me to find a site that said to mix washing up liquid and water put it in a spray bottle to spray the aphids every day.

BUT it didn't say if 'normal' washing up liquid was OK. I use a normal cruelty-free one, is that OK, or should I buy a particular type please, I don't want to damage the plant.

Thank you.